How are virus particles assembled and how do protein molecules move to build complicated structures, to send and receive signals, and to carry out many other biological functions? These are the broad questions of fundamental relevance to cancer biology that the proposed research on "Virus Assembly and Protein Adaptability" will explore. Polyomavirus assembly will be investigated by electron microscopy of the aggregates formed in vitro from mutant and wild type recombinant capsid proteins, by three-dimensional image reconstruction from cryoelectron micrographs of distinctive polymorphic aggregates, and by X-ray diffraction analysis of the disordered nucleohistone core structure in crystalline virions. The structure of the polymorphic stacked-disk aggregate of tobacco mosaic virus (TMV) protein will be determined by a combination of high resolution electron microscopy and electron fiber diffraction form oriented frozen hydrated specimens. Information about this structure, that of the crystalline four layers disk aggregate and the intact TMV particle will be correlated with physiochemical data to characterize the electrostatic interactions that regulate the virus assembly. The colloidal ordering of the rod-shaped virus particles will be investigated by optical and small- angle X-ray diffraction methods. The conformational variations of crystalline insulin induced by changes in solvent conditions will be determined by high resolution X-ray crystallography; and the average solvent structure will be mapped from accurate low-resolution data. The coupling in the atomic movements of the insulin molecules under various conditions will be determined by analysis of diffuse X-ray scattering measurements. Models of the fluctuating conformational substates of the protein molecule will be refined to fit the experimental diffuse scattering data and energetic restraints. These structural studies will involve technological developments in the measurement of X-ray scattering data using synchrotron radiation and advanced X-ray area detectors; preparation of well oriented samples for high resolution electron fiber diffraction; and application of computer graphics methods to analyze and display structural data.